A new report published by the Proceedings of the Royal Society of London B finds that temperature alone cannot account for early cherry tree blossoms, and light pollution from major cities also plays a role.

The research was put together by Spalding Associates, citizen scientists from the U.K. and The University of Exeter Penryn Campus, and found that buds were forming seven and a half days earlier than normal in areas with high amounts of artificial night-time light.

That could explain why Washington, D.C.’s famed Cherry Blossom trees have been blooming earlier, according to veteran meteorologist Anthony Watts. He points out that in a growing city, there’s more light now than in the past, potentially leading to earlier blooms of the cherry tree.

“Trees also respond to increased light, be it sunlight or light pollution from a growing and glowing city,” Watts wrote in a piece published Thursday on his blog Watts Up With That.

“We found that artificial lighting can accelerate tree leaves budding, and effectively the onset of spring by a week,” Professor Richard Ffrench-Constant of Exeter University wrote in a piece published on the university’s website.